In our copending application U.S. Ser. No. 031,368 and in copending application U.S. Ser. No. 095,870 filed concurrently, herewith, which applications are hereby incorporated by reference, there is described a process for drying and preheating free water containing glass batch agglomerates, preferably pellets, to an elevated temperature prior to melting. That process is especially uniquely adapted to drying and preheating hydrologically unstable agglomerates, that is free water containing glass batch agglomerates which, when attempted to be dried and preheated in a bed by direct contact with melter flue gases, or separately provided hot gases having a wet bulb temperature equivalent thereto, i.e., about 130.degree. F. to about 140.degree. F., convert or coalesce into process disabling aggregates during the drying operation.
When so dried with such gases having a wet bulb temperature of about 130.degree. F. to about 140.degree. F., a bed of hydrologically unstable agglomerates has an inherent or imminent aggregate forming height, below which no serious aggregation occurs, but this height is such as not to allow for the economic use of a shaft type preheater, or hopper, having a vertical bed of agglomerates therein to dry and preheat such agglomerates in a single processing operation. The application also discloses that the inherent, or imminent, aggregate forming height can be changed upwardly, to an adjusted imminent, or inherent, aggregate forming height, by decreasing the wet bulb temperature of the gaseous medium used to dry the bed of hydrologically unstable agglomerates. If melter flue gases are the gaseous combustion products used for drying, this can be done by diluting the flue gases with ambient air prior to passing them through a bed of the free water containing agglomerates; on the other hand if the gaseous drying medium is separately produced by the combustion of a suitable fuel, e.g., natural gas, the wet bulb temperature can be dropped below the 130.degree. F. to 140.degree. F. range by similarly diluting the combustion products or, more conveniently, by effecting such combustion with an excess of stoichiometric air. Even the adjusted inherent aggregate forming height corresponding to the use of a heating medium having a wet bulb of about 80.degree. F.-85.degree. F. is also such as not to economically allow a vertical bed of free water containing agglomerates to be dried and preheated in a single processing operation.
Exemplary glass compositions, which when agglomerated with water exhibit such hydrological instability, are the alkali metal oxide containing glasses and especially those containing Na.sub.2 O, on a dry, theoretical oxide basis, in excess of about 5 or 6% by weight. Commonly such glasses contain about 5 to about 25% Na.sub.2 O and are further exemplified by flat glass, bottle glass and fiberizable glasses which glasses typically contain about 10% to about 20% by weight Na.sub.2 O. The amount of water in such hydrologically unstable agglomerates is usually about 5% to about 20% by weight (dry basis).
The foregoing incorporated applications disclose a process for manufacturing glass from such type agglomerates wherein the agglomerates are dried and then preheated to an elevated temperature, e.g., to excess of 450.degree. C. or 500.degree. C., but short of causing the agglomerates to sinter or fuse together, and then charged to a glass melter at that elevated temperature for melting. Preferably the agglomerates are pellets having a size of about 1/4 inch to about 1 inch, desirably about 3/8-5/8 inch, with a water content of 10-15%. The process contemplates forming separate preconditioning beds of the agglomerates, which beds are at least partially dried to a hydrologically stabilized state and then the beds are discharged to a main vertical bed, which is maintained in a shaft type preheater, or hopper, where the agglomerates are heated to an elevated temperature and supplied to a glass melter for vitrification. Hot heating gases, e.g., combustion products, pass upwardly, directly through the main vertical bed, in counter-current flow to gravitationally downwardly moving agglomerates, to preheat them and then the gases are conveyed to preconditioning chambers to precondition static beds therein to a hydrologically stabilized state, i.e., a state where process disabling aggregates neither form in the preconditioning chambers nor subsequently in the shaft type preheater, or hopper. Preferably, plural preconditioning chambers are used with the beds being formed, preconditioned and discharged in a cyclic, sequential manner and in a generally parallel flow pattern. The height of the formed preconditioning beds is important and the process may be adjusted such that the bed height is less than the inherent aggregate forming height, less than the adjusted inherent aggregate forming height corresponding to the wet bulb temperature of the gases used for heating and drying, or greater than the adjusted inherent aggregate forming height corresponding to the wet bulb temperature of such gases used for preconditioning. It is contemplated that the wet bulb temperature of the combustion products, at least prior to being conveyed to the preconditioners, be decreased, as by dilution with air, to less than the wet bulb temperature of flue gases emanating from a fossil-fuel fired glass melter, e.g., to less than about 130.degree. F.-140.degree. F. Typically, the height of the preconditioning beds formed of the free water containing agglomerates will be between about 2 inches to about 9 inches.
An object of the present invention is to provide an improved glass manufacturing apparatus adapted to industrially exploit the above process.
Another object of the invention is to provide an improved apparatus for preconditioning hydrologically unstable glass batch agglomerates prior to supplying them to a hopper through which hot combustion gases from a melting furnace are passed.
Another object of the invention is to provide an apparatus for removing moisture from a batch of pellets above a bed of pellets in a hopper by passing hot gases through the bed of pellets and then through the batch of pellets so that the pellets may then be melted in a more efficient manner.
A further object of the invention is to provide an apparatus for preconditioning a bed of agglomerates, preferably pellets, above a vertical bed of pellets in a hopper and then physically dropping the pellets on top of the vertical bed of pellets in the hopper.
Still another object of the invention is to provide an apparatus for preconditioning glass batch agglomerates above a vertical bed of agglomerates in a hopper in a plurality of receptacles to which newly-formed agglomerates are supplied in a sequential relationship.
The general object of the present invention is to provide for an improved glass manufacturing apparatus. The apparatus recovers and beneficially employs otherwise wasted energy, it enhances environmental quality by recovering and recycling potential pollutants and provides for increased glass melter throughput with substantial fuel savings. Rather than requiring the use of massive equipment which consumes substantial amounts of precious floor space in a glass manufacturing plant, the present invention more economically employs small preconditioning chambers which allow for the operative, economic use of a shaft type preheating chamber to preheat agglomerates to an elevated temperature prior to melting. By mounting such preconditioning chambers adjacently above the preheating chamber, minimal floor space is consumed.
Many other objects and advantages of the invention will be apparent from the following detailed description.